That apparatus of student torture the 'Gnat longitudinal control system demonstrator', which taught us all about the Hobson motor, Scissor restrictors, Cam 'K', 'Q' gearing, Datum Shift, '399 Switches' etc was last seen mangled up as a so-called piece of art on the wall of the 'new' groundschool when the JP Mk 6 took over at Valley......and to think of how many folk had been through the agonies of trying to fathom out what all the bits did! It should have been preserved in a museum!